The invention relates to a method for handling a voltage drop in a control unit of a robot with a PC control of a combination of a real time operating system, for the time critical control and regulation of the robot movement, and only a time limited standard PC operating system for communicating with an operator where a battery/accumulator operation takes place in the case of a voltage drop.
The invention relates to a method for restarting a robot following the stoppage thereof due to a voltage drop.
In the case of a voltage drop or breakdown, it is known to terminate a program in a controlled manner by the buffer storage of electrical energy by means of an accumulator battery. Optionally, a mechanism controlled by the program, such as that of a robot, is also stopped in a controlled manner by utilizing stored buffer energy. Following voltage return, the control implemented by a computer has to be restarted and performs a so-called cold start, in which at the end of the starting process it is in the initial state as for a complete restart. In order that a robot can execute a problem and carry out its work, it must generally be initially moved by hand out of the component which it has been working. Its working program must be reselected and operated up to the break point and then work is continued following the restoration of the corresponding state. This procedure requires an experienced operator, it is fault-prone and in certain circumstances takes up a considerable amount of time. If a new workpiece is being machined, then the workpiece which has not been completely machined constitutes waste and is therefore also a cost factor.
Particularly with a PC-based control, the hardware and consequently the state of the working memory can only be buffer stored for a limited time by accumulator/battery buffering in the case of a voltage breakdown, so that an extensive automatic restoration of the stored control state following voltage recovery and start-up is only possible within a limited time, but not in the case of a longer voltage interruption. As the performance of a number of operating system processes is necessary for starting a conventional personal computer, this status in the cut-off or stoppage state cannot be readily transferred into the working memory.
The problem of the invention is to provide a method through which a plant or equipment stoppage is time-minimized and as far as possible waste resulting from the process interruption is avoided.
According to the invention this problem is solved in that initially in the case of a method of the aforementioned type a rotor movement taking place and optionally application operations are broken off or stopped in a clearly defined manner, that subsequently working processes of the control are terminated and that exclusively the contents of the working memory at the stoppage time concerning the real time operating system and robot control programs are stored in a mass memory.
The termination or controlled breaking off of the robot movement, etc. here means that the working process as such is not brought to an end and instead the working process is broken off, the movement as such is ended and the robot is stopped, but in a controlled manner, so that there is no danger or damage.
Therefore the important information concerning the status of the robot present in the working memory on stoppage as a result of a voltage drop are securely stored, so that such information is available for a random period of time independently of the electric power supply.
On this basis the invention also provides a method for the restarting of a robot stopped in this way, in which the standard PC operating system is loaded in the conventional manner into the working memory and started and the contents relating to the state of the real time operating system supplement or attachment and the robot programs in the end state are transferred from the mass memory or memories into the working memory and the control of the robot at the end state is resumed.
As a result of the invention the robot is integrated as a single installation or in cells or a larger union and at voltage recovery can seamlessly return to the interrupted program execution either automatically or under operator control.
According to a preferred development the contents of the working memory relating to the real time operating system and robot control programs are stored as an image in the mass memory or memories and that an image containing the state of the real time operating system and the robot programs is transferred from the mass memory or memories into the working memory. According to another development, on restarting the control of miscellaneous process peripherals in the end state is resumed, so that the entire process can be directly continued at the stoppage point.
Thus, according to the invention, only the working memory content relating to or containing the real time operating system with incorporated robot programs, e.g. VxWORKS are buffer stored in the mass memory or memories, but not the standard PC operating system, such as e.g. WINDOWS 95, 98 or NT. On restarting the standard operating system is started again in the conventional manner and the computer hardware is completely newly initialized. Subsequently the secured image of the real time operating system, particularly the robot programs is loaded back from the mass memory into the working memory, so that the control of the robot at the break point can be seamlessly continued. External communication interfaces to industrial working processes, such as those of further tools, particularly a welding or gluing device, etc. are restored to the state prior to interruption. The method according to the invention permits the use of standardized PC hardware, particularly with dynamic working memories i.e., dynamic random access memory (DRAM) for the control of robots and therefore reduces costs, also with respect to the software to be used.
In a preferred development of the method according to the invention, in the case of a voltage drop, the rotor movement is subject to braking close to the path. The control and regulation of the robot remains active until the stored motive energy has been consumed. This more particularly relates to electrical energy or power stored in the d.c. voltage buffer of the servoconverter (bank of capacitors) and optionally kinetic energy stored back in the same on braking.